This target tracker updates the probability density in Cartesian coordinates after each observation. Bearing estimates from several sonobuoys are used simultaneously by the tracker. The target speed need not be constant, but is assumed to be bounded above. No assumption is made about the direction of motion of the target. The predicted pdf is propagated in time uniformly in all directions. The target track generated is the one that maximized the a posteriori density after each observations. Results of tests done on both real and simulated data are presented to demonstrate the tracking capabilities of this method. Keywords include: Cartesian coordinates; Sonobuoys; Bearing estimates; Target speed; and Target tracks.